The invention relates to a stationary magnetron sputtering cathode for a vacuum deposition apparatus for substrates which pass in front of the cathode on a circular path and are disposed on a rotatable substrate holder. It comprises a target plate and a support plate which is disposed on a plane parallel to this target plate. It further includes a magnet system which is disposed behind the target plate and composed of plurality of permanent magnets. A first group or row thereof has the same polarity orientation and second group or row of magnets has an opposite polarity orientation so that a closed tunnel of magnetic flux lines starting at the first group or row and returning to the second group or row is formed above the target plate.
Magnetron sputtering cathodes are distinguished from those sputtering systems without the support of a magnetic field by a sputtering rate which is increased by the factor 10 to 30. This advantage, however, entails the disadvantage of an extremely irregular sputtering of the target plates since the constriction forced upon the plasma by the magnetic tunnel of magnetrons is reflected in a corresponding spatial restriction of the sputtering effect. The formation of an erosion trench where the lowest point lies below the culmination points of the magnetic flux lines requires that the sputtering be terminated after the sputtering of only 25 to 30% of the target material In stationary coating systems, i.e. those without a relative movement between cathode and substrates, this causes a very irregular distribution of the layer thicknesses. In principle, this means the erosion trench will be photographically, so to speak, reproduced on the substrates.
These problems along with a series of attempts to solve them are discussed in DE-OS 27 07 144 and DE-OS 36 19 194, to which U.S. Pat. No. 4,746,417 corresponds. The solution attempts include in particular a magnetron sputtering cathode where one single, self-contained magnet system in an eccentric position rotates behind a circular target plate (FIGS. 22 to 25 of DE-OS 27 07 144). The magnets form two nested, self-contained rows of magnets.
Further, from EP 0 365 249 A2 it is known (FIG. 6) in connection with a rotating sputtering cathode with a circular-disk like target plate to provide a number of the magnets in a row behind this plate so that the magnets form a non-symmetric loop and to provide the remaining magnets in an insular and contiguous manner in the center of the target plate. All the magnets of the row which form the loop are with their south poles aligned with the target plate, and those magnets joined in the insular arrangement are with their north poles directed to the target plate.
Further, it is known ("Vakuum-Information" issued by VEB Hochvakuum Dresden, Oct. 31, 1983, page 444, picture 1) to configure the target plate of a sputtering cathode as an approximately equilateral triangle and to dispose the magnets on the rear thereof in one row. Approximately parallel to two edges of this triangular plate and in the area of the third edge, this row of magnets follows an inwardly bound, bent path. Due to its special configuration, this cathode, referred to as a triangular plasmatron, permits quite a good distribution of the layer thickness on a substrate which passes in front of the target on a circular path.
Finally, from U.S. Pat. No. 4,631,106 (FIG. 7), it is known to place a plurality of magnets behind a rotating, circular-disk-like yoke plate in two spiral rows in such a manner that one row of magnets of the same polarity is located opposite a parallel row of magnets of the opposite polarity.